There is a need for dyes which have controlled solubility which would then allow their incorporation into cosmetic vehicles, without having them leech onto the other components of the formulation or emulsion, which could alter their optical properties. For example, the problem with many food dyes for use in cosmetics is that they are water soluble, which limits their use in cosmetics because they dissolve in perspiration and run.
Dyes are historically among the most widely used industrial chemicals, with applications for food, cosmetics, toiletries, and textile industries, to name a few. They impart a visual stimulus to consumers, and offer an enhanced psychological impact. While this is a mature field, there are still inherent problems associated with many dyes for cosmetic use due to their chemical nature. For instance, iron oxide is the primary colorant of rouge makeup, despite the availability of many organic dyes and pigments. The reason for this is many dyes are comprised of conjugated chromophores, which tend to aggregate, causing non-ideal color changes such as dullness, loss of color purity, and fluorescence quenching. Iron oxide on the other hand is stable. Many food dyes and D&C dyes that might therefore be considered for use are water soluble, which limits their use in cosmetics because they may dissolve in perspiration causing the cosmetic to run or leech out. There have been previous efforts to make pigments from water soluble materials that potentially migrate. For example, U.S. Pat. No. 6,630,019 shows mixing aluminum hydroxide with calcium phosphate slurry and then applying an FD&C dye mix. As used herein “FD&C” dyes and “D&C” dyes means any dye listed in Title 21, Part 82 of the Code of Fair Regulations, the content of which is hereby incorporated by reference. For example, U.S. Pat. No. 6,143,280 adheres FD&C dyes to silica and depositing alumina in the pores of the silica in order to resist dye migration.
Other techniques involve encapsulating dyes in order to prevent aggregation and to maintain the desirable spectral properties of the dye. For example, International Publication No. WO2006010728 of Feb. 2, 2006, describes the use of polymer microparticles of fluorescent whitening agents for use in cosmetics. Alternatively, large macrocycles such as cyclodextrins have been used to encapsulate chromophores non-covalently, and are commonly used as an additive when dyeing fabrics to enhance brightness. In these instances the dye and macrocycle form an inclusion complex; however only a certain number of dyes will fit in the cavity of the cyclodextrin. JP2006249012 describes fluorescent cosmetics by using molecularly encapsulated dyes, non-covalently bonded.
U.S. Pat. No. 7,150,764 of Dec. 19, 2006 describes the use of water-soluble fluorescent dyes and an insoluble conditioning agent for use in dyeing keratin fibers, whereas U.S. Pat. No. 6,753,002 of Jun. 22, 2004 teaches the use of fluorescent mineral powders with cosmetically acceptable vehicles to solve stability problems caused by moisture. Triazine-stilbene fluorescent brighteners have been reported (Dyes and Pigments, 2005, 63), as well as naphthol-triazine compounds as UV light absorbers as inhibitors for plastic degradation (EP1298126).
In all of the above approaches, to overcome the problem of stability to make cosmetic compositions that are cosmetically acceptable the approach has been adding things to the formulation to protect color; this changes the properties of the formulation and sacrifices some cosmetic elegance, as well increases expense. Thus, if wholly insoluble materials are used, caking can become a problem. If, on the other hand, encapsulation is used, sacrifice of color appearance may occur. These problems have limited the ability of any of these techniques to work easily with all FD&C and D&C dyes for cosmetics.
Accordingly, it can be seen that there is still a need for controlling dye solubility and for a methodology that meets current safety standards for each application, while allowing easy to manufacture dyes, which themselves have their properties controlled such that they are adaptable to current formularies while being cosmetically elegant, i.e., formulations that are stable, do not run or migrate, and which do not have color changes, such as dullness or loss of color when in use.
It is a primary object of the present invention to fulfill the above needs.
Another object of the present invention is to modify dyes themselves so that water solubility or lack of solubility are carefully controlled resulting in “tailor made” molecules, favorable for the cosmetic use in question. As a result, many FD&C and D&C dyes can now be used, where they could not otherwise be.